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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/**
* This VFS is built on top of the (unix|win32)-none, but it additionally
* sets any opened file as immutable, that allows to also open in read-only
* mode databases using WAL, or other journals that need auxiliary files, when
* such files cannot be created.
* This is useful when trying to read from third-party databases, avoiding any
* risk of creating auxiliary files (e.g. journals).
* It can only be used on read-only connections, because being a no-lock VFS
* it would be trivial to corrupt the data.
*/
#include "nsDebug.h"
#include "sqlite3.h"
#include "mozilla/UniquePtr.h"
#define ORIGVFS(p) ((sqlite3_vfs*)((p)->pAppData))
#if defined(XP_WIN)
# define BASE_VFS "win32-none"
#else
# define BASE_VFS "unix-none"
#endif
#define VFS_NAME "readonly-immutable-nolock"
namespace {
static int vfsOpen(sqlite3_vfs* vfs, const char* zName, sqlite3_file* pFile,
int flags, int* pOutFlags) {
if ((flags & SQLITE_OPEN_READONLY) == 0) {
// This is not done to be used in readwrite connections.
return SQLITE_CANTOPEN;
}
sqlite3_vfs* pOrigVfs = ORIGVFS(vfs);
int rc = pOrigVfs->xOpen(pOrigVfs, zName, pFile, flags, pOutFlags);
if (rc != SQLITE_OK) {
return rc;
}
const sqlite3_io_methods* pOrigMethods = pFile->pMethods;
// If the IO version is higher than the last known one, you should update
// this IO adding appropriate methods for any methods added in the version
// change.
MOZ_ASSERT(pOrigMethods->iVersion <= 3);
static const sqlite3_io_methods vfs_io_methods = {
pOrigMethods->iVersion, /* iVersion */
pOrigMethods->xClose, /* xClose */
pOrigMethods->xRead, /* xRead */
pOrigMethods->xWrite, /* xWrite */
pOrigMethods->xTruncate, /* xTruncate */
pOrigMethods->xSync, /* xSync */
pOrigMethods->xFileSize, /* xFileSize */
pOrigMethods->xLock, /* xLock */
pOrigMethods->xUnlock, /* xUnlock */
pOrigMethods->xCheckReservedLock, /* xCheckReservedLock */
pOrigMethods->xFileControl, /* xFileControl */
pOrigMethods->xSectorSize, /* xSectorSize */
[](sqlite3_file*) {
return SQLITE_IOCAP_IMMUTABLE;
}, /* xDeviceCharacteristics */
pOrigMethods->xShmMap, /* xShmMap */
pOrigMethods->xShmLock, /* xShmLock */
pOrigMethods->xShmBarrier, /* xShmBarrier */
pOrigMethods->xShmUnmap, /* xShmUnmap */
pOrigMethods->xFetch, /* xFetch */
pOrigMethods->xUnfetch /* xUnfetch */
};
pFile->pMethods = &vfs_io_methods;
if (pOutFlags) {
*pOutFlags = flags;
}
return SQLITE_OK;
}
} // namespace
namespace mozilla::storage {
UniquePtr<sqlite3_vfs> ConstructReadOnlyNoLockVFS() {
if (sqlite3_vfs_find(VFS_NAME) != nullptr) {
return nullptr;
}
sqlite3_vfs* pOrigVfs = sqlite3_vfs_find(BASE_VFS);
if (!pOrigVfs) {
return nullptr;
}
// If the VFS version is higher than the last known one, you should update
// this VFS adding appropriate methods for any methods added in the version
// change.
MOZ_ASSERT(pOrigVfs->iVersion <= 3);
static const sqlite3_vfs vfs = {
pOrigVfs->iVersion, /* iVersion */
pOrigVfs->szOsFile, /* szOsFile */
pOrigVfs->mxPathname, /* mxPathname */
nullptr, /* pNext */
VFS_NAME, /* zName */
pOrigVfs, /* pAppData */
vfsOpen, /* xOpen */
pOrigVfs->xDelete, /* xDelete */
pOrigVfs->xAccess, /* xAccess */
pOrigVfs->xFullPathname, /* xFullPathname */
pOrigVfs->xDlOpen, /* xDlOpen */
pOrigVfs->xDlError, /* xDlError */
pOrigVfs->xDlSym, /* xDlSym */
pOrigVfs->xDlClose, /* xDlClose */
pOrigVfs->xRandomness, /* xRandomness */
pOrigVfs->xSleep, /* xSleep */
pOrigVfs->xCurrentTime, /* xCurrentTime */
pOrigVfs->xGetLastError, /* xGetLastError */
pOrigVfs->xCurrentTimeInt64, /* xCurrentTimeInt64 */
pOrigVfs->xSetSystemCall, /* xSetSystemCall */
pOrigVfs->xGetSystemCall, /* xGetSystemCall */
pOrigVfs->xNextSystemCall /* xNextSystemCall */
};
return MakeUnique<sqlite3_vfs>(vfs);
}
} // namespace mozilla::storage
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